In the oil industry, it is necessary to obtain and analyze down-hole conditions, such as pressures and temperatures at various elevations. This has been done most commonly in the past by lowering electrically or mechanically operated gauge devices into the well, these gauges being either suspended on a wire line or fastened to available oil well tubular sections. By utilizing conductor wire lines, the information can be transmitted to the surface on a “real-time” bases. When non-conductor lines are employed, the gauge must be withdrawn to the surface so that the data can be either down-loaded to a plotter or read directly from an internally scribed chart, thus providing the operator with the desired information. In this process, whether the wire line is used as a suspension member or is strapped to the outside of tubular sections forming a string in the bore hole, damaging of the wire line is not uncommon. The damage or destruction of the wire line can occur when the string of tubular sections sticks within the bore hole, or when the wire line and/or tubing string is being run in or out of the hole. Not only is there the cost of the lost equipment, but such damage adds significantly to the cost of the operation because of the time involved in repairing the equipment and in fishing the equipment from the hole. The process of having to fish also includes the risk of endangering the well itself.
Other techniques have been developed for transmitting signals which are produced by apparatus located down-hole to the surface, including devices which develop and transmit signals electromagnetically to the surface. Such signals having been received by a receiving apparatus provide instantaneously information on the conditions sensed down-hole. This telemetry technique involves locating down-hole relatively complex equipment and providing a source of power. Structures have been developed for containing such equipment and power source. These structures enable the use of a portion of the tubing string to function as an antenna in the transmission of the signals to the surface. The process of using the tubing string, such as the upper portion of the string, as the antenna involves the provision of a connection which electrically isolates the upper portion from a lower portion of the tubing string so that the output voltage of the down-hole electromagnetic transmitters can be connected across terminals which are electrically isolated from each other.
The approach of using a telemetry technique for transmitting the information to the surface provides instantaneous readings at a set location of the down-hole sensing equipment and also avoids the use of a wire line. While having significant advantages over other techniques, problems due to the conditions which exist in the bore hole have in many respects hindered successful development in this process. For example, although there exists insulation couplers for use in an arrangement where the upper portion of the tubing is used as an antenna, such couplers have not always functioned satisfactory when the lower portion of the tubular string becomes jammed in the bore hole. This is not uncommon particularly where the lower part of the bore hole deviates from the vertical. Present insulation couplers have not been known to withstand the application of a high torque used in attempting to force the string when jammed, and a severing of the tubing string at the insulation connector results in the lower portion of the tubular string, which houses the expensive telemetry sensing and telemetry equipment, becoming completely disconnected at its down-hole position. Not only is the cost of the equipment involved, but there is the expense involved in reopening the hole and potential damage to the well.
Moreover, due to the nature of the sensing, power source and transmitting equipment utilized in the telemetry process and the extreme conditions to which th down-hole end of the tubing string is subjected, known methods of mounting such equipment has not always proved satisfactory. While the equipment must be protected, the manner in which it is carried and its connection to the insulation connector must be such that it is readily available for exchanging and servicing.
Yet another characteristic of some known structures incorporating an insulation coupler is that they are not capable of coping with particular conditions which can develope either above or below the test equipment when located down-hole. The down-hole test equipment is frequently used in conjunction with annular sealing packers, and in the known structures the insulation connector and/or the test equipment and mounting elements, together with the sealing packers in effect form a complete seal or blockage in the bore hole. Accordingly, in the event a pressure build-up develops either above or below the sealing packers, the tubing string can be sucked into or blown out of the bore hole. This can happen with sufficient force to cause severe injury to personnel and damage to equipment.